Nail polish, also known as nail varnish or lacquer, is a colorant applied to the nails to decorate and protect them. The polish comes in a wide range of colors and designs. It is claimed to improve the appearance of nails, encourage nail growth, strengthen them, and prevent breakage. It can be used as a base coat for artificial nails, and to cover up imperfections such as chips and smudges on natural ones. Some polish is advertised to cure fungal nail infections and to make fingernails grow faster.
The exact makeup of a particular brand of nail polish is often considered a trade secret. However, it is generally understood to contain several categories of ingredients: film forming agents, resins and plasticizers, solvents, and coloring agents. A number of other additives are sometimes included in the formula to enhance its characteristics. For example, thickening agents are added to keep the polish from being too runny, and to help it retain its shape after application. Some glitters are suspended in the polish to give it a sparkly look, and UV stabilizers (such as benzophenone) are used to prevent the colors from fading when exposed to light.
Most of the other ingredients in nail polish are held in a solvent that evaporates after application, leaving the colored film behind. This solvent is usually a volatile acetone, butyl acetate, or ethyl acetate. The type of solvent used determines how thick the polish will be and how long it takes to dry. Nitrocellulose, a form of cellulose, is a common film forming agent in nail polish. Resins and plasticizers are also used to provide a hard, glossy coating on the nail polish. The resins add depth and gloss, while the plasticizers reduce the risk that it will crack or chip. Common plasticizers are trimethyl pentanyl diisobutyrate and camphor.
Many of the chemicals in nail polish are potentially toxic and require strict safety precautions during manufacturing, testing, and packaging. Extreme attention to quality control is essential for both safety and consistency, since a single bottle of bad polish can lose a company customer forever. During the manufacturing process, subjective tests on the mixture and final product are made to check for various properties, such as smoothness of flow, gloss, hardness, and color. Objective laboratory testing of samples is also carried out throughout the manufacturing cycle.
Although nail polish is generally a cosmetic, some products are marketed to be therapeutic, and are therefore regulated by the Food and Drug Administration. The FDA can test and recall such products when there are concerns about their health effects. Nail polishes that are marketed as therapeutic treatments must be labeled as drugs, and must meet certain requirements before being sold. The FDA also requires that manufacturers perform testing and work with their suppliers to ensure the safety of these products (4). Vernis à Ongles